OK, thanks, I installed that, after tightening up the documentation a bit. Here's the documentation patch I installed.
--- autoconf.texi.~1.1120~ 2006-12-28 22:17:02.000000000 -0800 +++ autoconf.texi 2006-12-28 22:40:28.000000000 -0800 @@ -8252,8 +8252,15 @@ output. @defmacx AC_DEFINE (@var{variable}) @acindex{DEFINE} Define @var{variable} to @var{value} (verbatim), by defining a C -object-like macro for @var{variable}. @var{variable} should be a C -identifier that contains only letters, digits, and underscores. +preprocessor macro for @var{variable}. @var{variable} should be a C +identifier, optionally suffixed by a parenthesized argument list to +define a C preprocessor macro with arguments. The macro argument list, +if present, should be a comma-separated list of C identifiers, possibly +terminated by an ellipsis @samp{...} if C99 syntax is employed. [EMAIL PROTECTED] should not contain comments, white space, trigraphs, +backslash-newlines, universal character names, or [EMAIL PROTECTED] +characters. + @var{value} should not contain literal newlines, and if you are not using @code{AC_CONFIG_HEADERS} it should not contain any @samp{#} characters, as @command{make} tends to eat them. To use a shell variable, @@ -8276,6 +8283,10 @@ is obsolescent and may be withdrawn in f If the @var{variable} is a literal string, it is passed to @code{m4_pattern_allow} (@pxref{Forbidden Patterns}). + +If multiple @code{AC_DEFINE} statements are executed for the same [EMAIL PROTECTED] name (not counting any parenthesized argument list), +the last one wins. @end defmac @defmac AC_DEFINE_UNQUOTED (@var{variable}, @var{value}, @ovar{description})